In 4.2 you can no longer set server_name to NULL (which you need to do if you just want to set the codepage).  The problem is the code that was added to 4.2 to process server_name as an ARRAY.  In 4.1.2 the code looked like this (COM.c, line 486):

	if (server_name != NULL)
	{
		if (Z_TYPE_P(server_name) == IS_NULL) {
			server_name = NULL;
		} else {
			if (!INI_INT("com.allow_dcom")) {
				php_error(E_WARNING, "DCOM is disabled");
				RETURN_FALSE;
			} else {
				convert_to_string_ex(&server_name);
			}
		}
	}

In the 4.2.0 COM.c, the new flags variable set and IS_ARRAY check was added before the IS_NULL check, instead of inside the else branch - thus flags is set to remote invocation, even if server_name is NULL.  To fix this I moved everything below "if (server_name != NULL)" and above "if (Z_TYPE_P(server_name) == IS_NULL) {" to after "} else {".